Repairing a split chair leg

I have a chair that was brought into my shop with a back leg whose rear bottom was broken out from a caster's stem that had gotten angled backwards. As of now I have repaired this initial problem with a "u" type joint epoxied together such that the long grain surface area is greater than the cross grain joint area. I thought about dowels in the cross grain bonds, but this would be very difficult to accomplish and the results wouldn't be very precise in my estimation. This is partly due to the curved profile of the rear leg.

As a result of the initial fracture, under stress, the adjacent front leg has a stress fracture in the front that travels up the leg about 60% of the total length of the leg. There is also a deeper crack on the back side of the leg that is about 1/2" long. These were caused by a worn hole bored out for the caster's wood stem.

The customer seems to want the chair sitting up on 2 1/2" high casters as per the original design.

I'm thinking that there are 2 options for me:

First option would be to cut off the chair leg above the long stress fracture and attach a new leg portion, either by doweling the two pieces together, or again forming a "u" type joint and epoxying the joint together. The front leg is merely tapered on 3 sides about 3/4 the way up the leg.

Second option would be to carefully undo the upholstery and try to take apart the leg/frame joint and do a total reconstruction of the leg.This would be a lot of work and of course fairly expensive to the customer.

So... with all the above history my questions are:

What would be your philosophy of repairing the front leg?

Are my options reasonable?

What would be the best way of pulling the front leg/frame joint apart? If it came to that.

(post #125361, reply #1 of 2)

Your options sounds reasonable to me. But without seeing the chair in question, it’s difficult for me to guide you in specific ways of repair. Jobs like these always depend upon the specific type of chair, the specific type of damage involved, and sometimes the type of wood. Having said this, let me throw out some options I’ve tried, and see if that helps you with the job at hand.

First, many deep cracks can be repaired readily by gluing them back together. If you can close the cracks with moderate pressure from a clamp or clamps, and they fit together well, then by all means shove some white or yellow glue in there and clamp it up. If, however, the cracks are more severe, and closing them with clamps leaves gaps, then try adding a new slip of wood into the recess. First widen the crack if necessary with a handsaw or a sharp knife guided by a straightedge, then carefully dry-fit the replacement piece, and glue and clamp it in place. Once the glue has dried, the repair should be stronger than the surrounding wood.

If a new leg piece is required, consider using a scarf joint for the leg repairs. Essentially a really long miter joint, a scarf provides a lot of long grain-to-long grain gluing surface, which means the joint is more likely to hold up over time compared to a U-type assembly, and definitely light-years longer than some sort of dowel joint, which is primarily an end grain-to-end grain joint. You can rough-saw the original leg scarf with a handsaw, then plane or file it flat and smooth. Cut the replacement scarf on the bandsaw, and plane that smooth, too. The joint only works if both parts are flat and smooth. Glue it up with rubber bands, old bicycle inner tube, or surgical tubing, placing even and moderate pressure all around the joint.

Finally, taking apart the damaged leg might be less work than you think. Removing and adding new staples in the upholstery is well within the realm of the woodworker, and shouldn’t cause you much trouble at all. Once you’ve removed the seat, study the leg-to-rail joint: It’s probably a mortise and tenon, or perhaps it’s doweled, both of which are housed joints that can’t easily be accessed. If you can’t get at the joint itself, try injecting some steam (as best you can) into the joint area to loosen the adhesive. Or try pouring on some white vinegar if you can’t get access to steam. Failing that, try some hot water. You should be able to loosen the glue enough that you can wiggle and gently pry apart the joint. If you need more than wiggle power alone, try gentle taps from a deadblow mallet, or use a small hammer over a small block of wood.

If the chair was made prior to around 1950, it should practically fall apart after this treatment, since hide glue is most likely holding it together. But even modern white and yellow woodworking glues respond reasonably well to the treatments described above. Remember to look for any cross pins or dowels, and remove them first before wiggling or tapping on the joint. And you might have to remove the entire side rail (or the front, if it’s easier to do so) so that you can remove the leg without further breakage, which will also make it easier when it’s time to put the new leg on.

Once the leg is off, clean up what should be either a tenon or a pair (or more) of dowels on the front and side rails, removing all the glue residue. If the chair is old and joined with hide glue, you don’t have to be so fussy. Just scrape away any powdered glue and smooth the surface. Then make your new leg, cutting mortises to fit the newly-exposed tenons. Glue and clamp, and you’re done.